University of Arizona scientists in the next week or two will begin field work on an international project to core 1.8 kilometers into an immense crater created by the impact of an asteroid or comet 65 million years ago.

The Cretaceous-Tertiary (K/T) impact is thought to have led to one of the greatest mass extinctions in Earth history, including dinosaur extinction.

The impact generated ten thousand times more energy than in the world's nuclear arsenal, and six million times more energy than the 1980 Mount St. Helens volcanic eruption.

The project, the Chicxulub Scientific Drilling Project (CSDP), is located near Mérida, Yucatan, Mexico.

"This is a very special collaboration with our neighbors in Mexico and highlights the success of international cooperation among scientists throughout the world," said David A. Kring, UA associate professor of planetary sciences and co-investigator in the CSDP. "We appreciate the opportunity to work with our colleagues from UNAM and ICDP member-nations."

"The hypothesis that a meteorite impact caused the demise of the dinosaurs and consequently, perhaps paved the way for mammalian evolution has been one of the most important recent findings in Earth sciences," said UA College of Science Dean Joaquin Ruiz, professor of geosciences. Discovering what the object was and the details of the impact "is very important," he added. "The fact that the University of Arizona has one of the leading investigators in the field testifies to the quality of science that goes on at this institution."

Ruiz and Rene Drucker, UNAM coordinator of scientific investigation, signed a memorandum of understanding in Mexico on Tuesday that will facilitate and pay for the exchange of students and faculty on this project and future projects involving UA College of Science departments.

The Chicxulub Scientific Drilling Project is being run under the auspices of the International Continental Scientific Drilling Program (ICDP), headquartered in Potsdam, Germany. In addition to Mexico, Germany, and the United States, nations funding ICDP operations include Canada, China, Japan and Poland. Corporate affiliates include UNESCO, the international Ocean Drilling Program and Schlumberger Inc.

Kring and undergraduate geosciences major Jake Bailey will join operations at the Yaxcopoil-1 site 40 kilometers southwest of the province's capital, Mérida. Ruiz will visit the site in a few weeks on a future trip to Mexico.

Workers cleared the site of vegetation, constructed a well to supply water to the drilling rig, and installed the drilling rig in November and early December. The governor of Yucatan, UNAM scientists and officials, and a German delegation inaugurated the project with opening ceremonies on Dec.3. Actual drilling began Dec. 12, and the crew reached impact breccias -- rock of sharp-angled fragments -- late last week.

"We expect to reach the 1.8-kilometer (one and one-tenth mile) depth after 69 days of drilling," Kring said, at a cost of $1.5 million from the ICDP.

"We planned to hit rocks in the crater between 500 meters (1,640 feet) and one kilometer (3,280 feet), then continue through the impact crater itself -- through breccias and the impact melt layer -- all the way down to continental crust bedrock. If we succeed in getting more funds, we'll core down to 2.5 kilometers (1 and a half miles)," he added.

The hypothesis that an asteroid or comet impact caused K/T mass extinction was first proposed in 1980 by Nobel laureate Luis Alvarez, his geologist son, Walter, and others at the University of California-Berkeley.

Kring was one of seven scientists who confirmed the highly controversial theory in the early 1990s.

During oil exploration, PEMEX geophysicists Antonio Carmargo-Zanoguera and Glen Penfield identified the Chicxulub structure as a possible impact crater. Alan Hildebrand of the University of Calgary (then a UA graduate student), Kring, and UA planetary sciences professor William Boynton, working with Penfield, Carmargo-Z., Mark Pilkington of the Canadian Geological Survey and Stein Jacobsen from Harvard University, confirmed with petrologic and geochemical studies that the 180-kilometer (110-mile) diameter Chicxulub structure was indeed formed by giant asteroid or comet impact.

Scientists will analyze cores for details on exactly how the Chicxulub impact suddenly and catastrophically changed Earth's environment and ecology, killing more than 75 percent of the plant and animal species on land and in the oceans.

At the Yaxcopoil-1 site, a professional drilling crew uses a diamond-tipped drill to extract 64mm-diameter (2 and a half inch-diameter) core in segments up to 6-meters (19 and a half feet) long. Core segments are placed on a bench at the work site.

UNAM staff and students -- soon to be joined by the UA team -- then wash, label, measure and box the cores. The boxed cores are processed on site and at a laboratory in Mérida, where cores also are scanned as digital images that Kring and other scientists can view over the Internet.

Kring, his students, and researchers from other institutions will be able to further analyze the core samples at the Lunar and Planetary Laboratory and other labs after the drilling is complete.

Kring's work on the Chicxulub impact crater and K/T boundary mass extinction event has been supported by NASA, the National Science Foundation, ICDP, and the University of Arizona.